As a high-density recording technique for holograms, for example, there is JP 2004-272268 A (Patent Literature 1). Abstract of this literature discloses as follows: A multiplexing method and apparatus that allows holograms to be spatially multiplexed with partial spatial overlap between neighboring stacks of holograms. Each individual stack can additionally take full advantage of an alternate multiplexing scheme such as angle, wave length, phase code, peristrophic, or fractal multiplexing. An amount equal to the beam waist of the signal beam writing a hologram separates individual stacks of holograms. Upon reconstruction, a hologram and its neighboring holograms will all be readout simultaneously. A filter is placed at the beam waist of the reconstructed data such that the neighboring holograms that are readout are not transmitted to the camera plane. Alternatively, these unwanted reconstructions ban be filtered out with an angular filter at an intermediate plane in the optical system that has a limited angular pass band.
Furthermore, Abstract of JP 2014-53069 A (Patent Literature 2) discloses as follows: An optical information recording/reproducing apparatus for recording information using holography including a signal generation section which generates two-dimensional data by a two-dimensional encoding method in which a lower limit value of the number of consecutive ON/OFF pixels in an array in one direction of the pixels in a two-dimensional spatial light modulator is K (K≥2, K: a natural number) and a pickup which records the two-dimensional data generated by the signal generation section on a hologram disc can solve the problem.
As an equalization technique for reproducing holograms, for example, there is JP 2006-267539 A (Patent Literature 3). Abstract of this literature discloses as follows: An eliminator includes a pixel extractor 101 which extracts a target pixel and peripheral pixels of the target pixel from a read digital image, a filter 102 which inputs the target pixel and the peripheral pixels and eliminates noise of the target pixel, and a first coefficient selector 105 which selects a filter coefficient for the filter 102 from a first coefficient memory 104 based on a pattern of binarized data subjected to temporary determination and inputs the filter coefficient to the filter 102, and the noise caused by interference from the peripheral pixels can be eliminated by filtering according to the pattern of the peripheral binarized data by the filter 102.